The correct answer is C) Lower than normal suction pressure. A small obstruction at the thermostatic expansion valve inlet will restrict the flow of refrigerant into the evaporator, leading to a lower than normal suction pressure. This is because the expansion valve is responsible for metering the proper amount of refrigerant into the evaporator based on the load. An obstruction at the inlet will limit the amount of refrigerant entering the evaporator, resulting in a lower suction pressure. The other options are incorrect because: A) Higher than normal discharge pressure is not a direct result of an obstruction at the expansion valve inlet; B) Expansion valves are not designed to pass all foreign particles, and an obstruction can adversely affect operation; and D) Ice formation is not the sole cause, and it will not necessarily melt due to superheat without addressing the underlying issue of the obstruction.